Data from: The price of looking sexy: visual ecology of a three level predator-prey system

Colour signals and colour vision play a pivotal role in intraspecific
communication and predator-prey interactions. However, the costs of
expressing conspicuous sexual signals at multiple trophic levels have been
largely overlooked. Sexual signals can also experience character
displacement in sympatric populations of closely-related species, leading
to potential changes in conspicuousness. We here investigate a
bird-damselfly-fruit fly predator-prey system, where two closely related
damselfly species have conspicuous, sexually selected wing coloration. The
damselflies can occur in sympatry and allopatry and reproductive character
displacement in the coloration size has been previously reported. We
quantify the damselfly wing reflectance from replicated sympatric and
allopatric populations, and use receptor noise models to investigate the
visual discriminability of the wing coloration for the bird, damselfly and
fly vision systems, against natural backgrounds. We perform
electroretinograms to study damselfly eye sensitivity. We also estimate
damselfly predation risk in natural populations. We find that the
chromatic component of wing coloration makes males highly discriminable to
the predator, but not to the prey. However, female wing coloration is
predominantly cryptic for the predator and prey, and interestingly, also
for male damselflies. A female being cryptic to conspecifics likely
reduces male harassment. The estimates of predation risk partially support
the discriminability results. We also show that there is no difference in
colour vision sensitivity between the two damselfly species and sexes, and
no difference in wing coloration or its discriminability between sympatric
and allopatric populations. Our results suggest that sexually selected
traits can be antagonistically selected by predators and prey, and that
this antagonistic selection can be sex-dependent: males are paying a large
cost in terms of conspicuousness, while females remain mostly cryptic. Our
study thus emphasizes the need for investigating visual communication at
multi-trophic levels since the degree of colour discriminability can
differ between predators, prey and the focal species.